Transition metals Flashcards
What are the d-block transition metals?
Metals with an incomplete d sub shell in at least one of their ions.
The filling of the d orbitals follows the aufbau principle, except…
Chromium and copper atoms.
Why are chromium and copper exceptions?
Due to the special stability associated with the d subshell being half filled or filled.
Zinc and scandium are not transition metals because…
They have full electron shells in all their ions.
An element is said to be on a particular oxidation state when it…
has a specific oxidation number.
Uncombined elements have an oxidation number of
0
Ions containing single atoms have an oxidation number that is…
The same as the charge on the ion.
Oxygen has an oxidation number of?
- 2, except in peroxides where it has an oxidation number of -1
Hydrogen has an oxidation number of?
+1, except when in a metal hydride where it is -1.
The sum of all the oxidation numbers of all the atoms in a neutral compound must add up to?
0
The sum of all the oxidation numbers of all the atoms in a polyatomic ion must be…
Equal to the charge on the ion
Compounds of the same transition metals in different oxidation states may have…
Different colours.
What is oxidation?
Increase in oxidation number.
What is reduction?
Decrease in oxidation number.
Changes in oxidation number of transition metal ions can be used to…
Determine whether oxidation or reduction has occurred.
Compounds containing metals in high oxidation states are often?
Oxidising agents.
Compounds containing metals in low oxidation states are often?
Reducing agents.
What are ligands?
Negative ions or molecules with non-binding pairs of electrons that they donate to the central metal atom or ion forming dative covalent bonds.
Ligands can be classified as ?
Monodentate, bidentate up to hexadentate
Monodentate ligands provide — electrons.
1
Bidentate ligands provide — electrons.
2
Hexadentate ligands complex in ——— ratio.
1:1
What is the coordination number?
The total number of bonds from the ligands to the central transition metal.
Coordination number and shape?
2 = ?
Linear
Coordination number and shape?
4 = ?
Square planar or tetrahedral
Coordination number and shape?
6 = ?
Octahedral
Are the d orbitals degenerate in a complex of a transition metals?
No
When does splitting of d orbitals to higher and lower energies occur?
When the electrons present in approaching ligands cause the electrons in the orbitals lying along the axes to be repelled.
Strong field ligands?
Cause a large difference in energy between subsets of d orbitals.
Weak field ligands?
Cause a small energy difference between subsets of d orbitals.
Spectrochemical series
I⁻ < Br⁻ < Cl⁻ < F⁻ < OH⁻ < H₂O < NH₃ < en (ethylenediamine) < NO₂⁻ < CN⁻ < CO
Colours of many transition metals can be explained in terms of?
d-d transitions.
Light is absorbed when electrons…
Electrons in a lower energy d orbital are promoted to d orbitals of higher energy.
If light of one colour is absorbed then…
The complementary colour is exhibited.
Electrons transition to higher energy levels when
Energy corresponding to the UV or visible regions of the EM spectrum is absorbed.
What does changing the ligand do?
Changes the split between d orbitals and therefore will change the colour.
Transition metals and their complexes can act as?
Catalysts.
Heterogenous catalysts?
Are in a different state to their reactants.
Heterogenous catalysis (chat GPT)
Reactant molecules adsorb onto active sites, where unpaired d electrons or unfilled d orbitals in transition metals help form activated complexes. This provides an alternative pathway with lower activation energy, increasing the reaction rate.
Homogenous catalysts?
In the same state as reactants.
Homogenous catalysis (chat GPT)
Effective because they can change oxidation states, allowing them to form intermediate complexes with reactants. This stabilises transition states and provides an alternative reaction pathway with a lower activation energy.
